Photosynthesis is actually oxidation reduction process in which water is oxidised and \(\mathrm{CO}_2\) is reduced to carbohydrates. Assimilatory power ATP and \(\mathrm{NADPH}_2\) are required for reduction of \(\mathrm{CO}_2\). But this reduction is independent of light i.e occurs in presence or absence of light but production of assimilatory power is light dependent. This reaction is called light reaction or Hill's reaction and the light independent phase is an enzymatic reaction called dark reaction. It occurs is stroma of chloroplast and is enzyme radiated one. It was first of all established by F.F. Blackman and so is also called Blackman's reaction. During this process \(\mathrm{CO}_2\) is fixed to carbohydrate.